The invention relates generally to printing presses, and more particularly to the control of ink fountains for providing ink to a plate cylinder.
In typical color printing,. a color image to be reproduced by the printing press are separated into four component colors. Four printing plates are made from these separations. The printing plates then are placed on the plate cylinders of four separate printing units of the printing press, for providing black, cyan, magenta and yellow ink to the respective plates. As a web or sheet of paper runs through the press, the combination of the four inked images should accurately reproduce the image which is to be printed by the printing press.
Typical printing presses have a series of individual ink fountains which extend across the width of the print cylinder to deliver the proper amount of ink to the printing plate. Each fountain thus represent a xe2x80x9cstripxe2x80x9d of one of the colors along the width of the image or plate. A remote ink key adjustment is provided at a console, so that a press operator can adjust the corresponding individual ink fountains to deliver more or less ink to each strip of the plate.
Each printing plate may contain a plurality of images, for instance eight images, each image representing a page of a magazine. When a press prints on both sides of a web of paper, there then might be sixteen pages printed during a single run of the press. The printed web is then cut into sheets. The sheets are then folded into signatures so that the pages are properly ordered.
The operator views images on a signature printed from the printing press, compares it with the original images, and adjusts the ink fountains. He uses the keys to deliver, for example, more yellow ink to an outer strip of the image, or more magenta to a middle strip. If there are many pages in a single signature, the operator typically will view only two images or pages of a signature at a time by laying the image on an operator console.
This process can be long and complicated, especially when several images or pages are located on a single signature. The operator must identify the image to be corrected (for example by page number), and where the image to be corrected is located on the printing plate so that the corresponding keys are properly aligned with the printed image. Only then can the operator select the proper keys to adjust the ink fountains in the press. Especially if the images are of similar color or have similar designs, the process of identifying a signature, and its proper location above the keys on a control console, can be time consuming and frustrating for the operator.
The present invention provides for automatic identification of the image to be corrected by comparing stored digital images of an initial sample with the actual signature images from the printing press. The pages can thus be quickly and easily identified. Moreover, by identifying the location of the signature image on the console surface, the system of the present invention can automatically choose the ink fountain set which is to be adjusted. The operator need not align the signature on the console.
The present invention therefore provides an apparatus for remote ink control fountain selection comprising a video camera for reading a signature image, an image digitizer, an image comparator for comparing the signature image to a sample image set and a memory device for storing the sample image set in digitized form.
A method for remote ink fountain selection is also provided comprising the steps of digitizing sample images and providing each said sample image with an identification; digitizing a printed signature image from a printing press which corresponds to at least one of the sample images; comparing the digitized printed signature image to the digitized sample images; and outputting the identification of the digitized sample image upon a match with the digitized signature image.
The digitized sample image and the digitized signature image of this method may be only part of the actual image which is reproduced by the printing press, for example the upper right comer of the actual image.
The apparatus and method permit the image on the signature to be quickly and easily identified, so that it can be compared with the sample image, thus reducing operator error and set-up time.
Moreover, the image comparator can be connected to a fountain control box to automatically set the fountains to be adjusted based on the page number or other identification of the signature image on a console surface. This eliminates the need for the operator to properly align the signature above the keys.